Report: WR Manningham has season-ending knee injury

As it turns out, the worst loss of the Jim Harbaugh era also included the loss of the 49ers’ No. 2 wide receiver.

Mario Manningham sustained a torn ACL and PCL in his left knee in Sunday’s 42-13 drubbing at Seattle, according to ESPN. Manningham is the fourth Niner in the past five games to suffer a season-ending injury, joining running back Kendall Hunter, wide receiver Kyle Williams and backup defensive tackle Demarcus Dobbs.

In addition, All-Pro defensive tackle Justin Smith (elbow) missed his first start since 2001 on Sunday and it’s not clear if he’ll be available for the postseason.

Manningham, who missed the two games prior to Sunday’s contest with a shoulder injury, ranks second on the team in receptions (42) and third in yards (449). He had established a solid rapport with Colin Kaepernick, who had completed 13 of 17 passes for 151 yards when targeting the five-year veteran.

With Manningham and Williams out, the 49ers receiving corps features Michael Crabtree, Randy Moss and Ted Ginn, who has played sparingly on offense and has two catches for one yard. Tight end Delanie Walker actually lined up at wide receiver instead of Ginn on Sunday after Manningham exited. First-round pick A.J. Jenkins has been active for three games and does not have a catch this season,

San Francisco does have two wideouts on its practice squad with NFL playing experience in Chad Hall and Ricardo Lockette.

Hall, 26, a 5-foot-8, 187-pound slot receiver, had 14 catches for 135 yards and two touchdowns with the Eagles from 2010-11. Lockette, 26, had two catches for 105 yards, including a 61-yard touchdown, with the Seahawks last year. Lockette ran a 4.37-second 40-yard dash at the 2011 combine, which matched the fastest time by a wide receiver.